Prospekt Flora, Intresting facts

A community of thyme and other plants on a rocky pasture overlooking Baška in the southern part of Krk Island. The chemical components emitted by thyme may have a positive or negative effect on microbial communities in the soil and on neighbouring plants in the community. (Photo by Marko Randić)

Different types of thyme blossom mainly in the spring or summer, depending on the altitudes above sea level and the plant communities in which they grow. Interestingly, the specific chemical composition of the dead and fallen leaves of thyme, which accumulate on the surface of the soil usually before winter, has an effect on other organisms. This phenomenon is called allelopathy.


Several species of thyme (Thymus sp. div.) can be found in our region. They grow in sunny spots, typically on shallow and rocky soils, from the islands and sea coast to the highest mountain tops such as Učka, Risnjak and Snježnik. They create associations with other plant species in a variety of different grassland communities, ranging from rocky pastures and dry grasslands in lowlands to pre-alpine turfs in mountains. Characteristically, the oil glands in the leaves, stems and calyces of these plants contain considerable amounts of essential oils.

The composition and quantities of essential oils vary from species to species. The type and quantity of the individual components in the oil may change slightly during the plant’s development cycle and during the seasons of the year. The essential oils in the fallen leaves of thyme affect the germination ability of certain plant species growing nearby. The components of the plant’s essential oils may sometimes have a strong effect on those plant species that do not grow alongside thyme in nature. If we were to plant them in soil containing traces of the oils or components washed out from thyme leaves, the growth of such plant species could be stunted. Recent studies have shown that this in particular refers to certain species of cultivated plants.

The essential oils of aromatic plants, including thyme, also affect microbial communities in soils by increasing soil respiration, thus fostering the growth of microorganisms (in particular, the bacterial components of microbial communities) that use essential oils as a substrate for growth. The ability of an organism in soil to enable or constrain the growth and development of another organism is called allelopathy.

Topics: plants (botany), phytochemistry, ecology, International Year of Soils

Keywords: thyme, Thymus, allelopathy, microbial communities


Thyme growing along the edges and in the small cracks of a glacial erratic in the Veli Pribiniš meadow on Mt Platak. The plant’s specific chemical components affect microorganisms and (most likely) lichens as well as the other plants growing on the surface of the erratic, in its cracks or along its edges. (Photo by Dinko Dorčić and Marko Randić)